Final answer:
The first step to securing a SOHO wired network is to change the default usernames and passwords, which is crucial to prevent unauthorized access.
Step-by-step explanation:
The first step to securing a wired network after installing the hardware is to change the default usernames and passwords on all network devices. This step prevents unauthorized access to your network by ensuring that the default credentials, which are often easy to guess or publicly known, are replaced with strong, unique usernames and passwords.
Other steps such as enabling MAC filtering, disabling unused ports, and assigning static IP addresses contribute to security, but these are typically undertaken after changing the default login credentials. A network is only as secure as its weakest link, and unchanged default credentials are a well-known vulnerability.